The present invention relates to a vehicle control apparatus and method, and more particularly to a vehicle control apparatus for a vehicle in which an electric generator and an automatic transmission including a hydraulically controlled clutch are provided along a power transmission system or a drive train, in that an engine is controlled so as to be automatically stopped and restarted.
It frequently happens that vehicles have to stop while being driven in towns and at intersections. In case vehicles have to stop like that, since fuel continues to be consumed as long as the engine is running, there is caused a drawback that the fuel consumption gets worse. With a view to solving the drawback, there has been proposed a vehicle provided with an automatic stop and restart system for improving the fuel consumption by automatically stopping the engine when the vehicle stops temporarily and restarting the engine when the vehicle starts off (JP-A-6-257484). This automatic stop and restart system controls such that the engine is automatically stopped when a predetermined automatic stop condition is met where for example, the accelerator pedal has not been depressed for a certain period of time while the engine is running and is then automatically restarted when a predetermined automatic restart condition is met where for example, a start-off operation is attempted while the engine is automatically being stopped.
In addition, among vehicles there are so-called hybrid vehicles in which an engine and an electric generator (motor) connected to an engine output shaft are provided. In the hybrid vehicles, the startability of the vehicle is improved by an assist amount provided by a motor assist control of the electric generator. Among the hybrid vehicles of this type there are hybrid vehicles which include the aforementioned automatic stop and restart control system and an automatic transmission in which a clutch control for engaging and disengaging a clutch and a shift control for shifting gears are hydraulically implemented.
Incidentally, an oil pump for sending an oil pressure to an automatic transmission is normally driven by virtue of the revolution of a crankshaft of an engine. Due to this, when the engine stops, the oil pump also stops, and the oil pressure sent to the automatic transmission lowers. This has been causing a problem that when a vehicle is attempted to move from a standstill after the engine is restarted, there is caused a delay in raising the oil pressure that is sent to the automatic transmission, and less load is applied to the engine to thereby cause a drastic engine speed increase, while when the oil pressure to the engine is raised thereafter and the clutch is engaged, an engagement shock which is brought about by the engagement of the clutch is caused in the vehicle.
While a proposal has been made against the problem of drastic engine speed increase in which the drastic engine speed increase is restrained by the electric generator (Japanese Patent No. 3011069), nothing is mentioned therein on a countermeasure against the engagement shock caused when the clutch is engaged. In addition, although there has been proposed a method in which an electric oil pump is provided separately, so that the electric oil pump is driven to produce an oil pressure for engagement of the clutch while the engine is automatically stopped (JP-A-8-14076), this method has caused a drawback that electric power consumption is increased.